Miniature switches of the so-called "dualin-line package" (DIP) design, for which the switch of the present invention is readily adapted, are well known in the electronic's field. An assembly of a multitude of such individual switches which can be operated independently from one another are commonly mounted on a printed circuit board having two rows of mounting holes of standardized configuration. The switch leads are soldered to the foil side of the board thereby providing for the electrical connection of various circuits disposed on the circuit board.
Such known switches have been of a cam operated design as represented by U.S. Pat. Nos. 3,878,344 and 3,883,705 or have utilized a slide actuated configuration as shown by U.S. Pat. Nos. 3,849,610; 3,917,921; 3,974,346; 4,012,608 and 4,092,504.
In order to reduce assembly costs, such switches are generally mounted on the printed circuit board by a technique known in the electronic's industry as wave soldering. With such a technique, the printed circuit board with the switch positioned thereon is carried by a conveyor to a molten solder bath which is brought into contact with foil side of the circuit board. In this manner the switch terminal leads which protrude through the foil side of the circuit board are joined by the solder to the foil thereby completing the electrical circuit therebetween.
However, due to the contamination caused by the oils and fluxes used in this process, many of such DIP switches are sealed in order to protect their switching contacts. Such sealed switches are usually epoxied at their terminal base and taped over the top, actuator portion thereof. The tape is removed after the soldering process.
In addition to its added expense, this procedure has led to numerous problems affecting the reliability of the switches. For example, a slight leak in the sealed switch would permit the cleaning solvents used in the process to enter the switch and deposit contaminants on the contacts which would be impossible to remove. Furthermore, the sealed design of the switches may produce out-gassing problems from the plastic materials used in their construction due to the high temperatures used in the process. Likewise, due to their sealed design, it is impossible to inspect the switches prior to soldering them on the circuit board, thereby increasing the likelihood of a defective switch being installed in the component system which is relatively expensive to remove once the assembly process is completed.
A further problem associated with prior DIP switch designs is that they have a high failure rate due to defective contact operation. This problem is due to the miniature design of the switch which requires the use of extremely small and thin contact terminals. Hence, unless the contacts are precisely aligned with respect to each other, a reliable electrical connection between them cannot be achieved.
In order to overcome this problem, DIP switch contact designs such as are shown in U.S. Pat. Nos. 3,974,346; 4,012,608 and 4,092,504 have been developed to achieve positive contact operation. These switches utilize a separate, downwardly biased bridging element to electrically connect the contact terminals which are mounted on the circuit board. Although such switches are more reliable in their operation, they are also more complex and expensive to manufacture. An additional inherent disadvantage of such a design is that two independent electrical connections must be established within the switch in order to electrically connect the contact terminals. That is, the bridging element must establish electrical contact with both contact terminals in order to complete the electrical circuit through the switch. Hence, this factor doubles the possibility for failure of the switch due to one or the other of the contact terminals becoming contaminated or being out of alignment with the bridging element.